Status and Very First Commissioning of the Astrid2 Synchrotron Light Source S.P

Home , ASTRID2, Beamline, Insertion device, Undulator

MOPEA003 Proceedings of IPAC2013, Shanghai, China

STATUS AND VERY FIRST COMMISSIONING OF THE ASTRID2 SYNCHROTRON LIGHT SOURCE S.P. Møller#, N. Hertel, J.S. Nielsen, ISA, Aarhus University, DK-8000 Aarhus C, Denmark

Abstract The new Danish light source, ASTRID2, to provide 6 brilliant UV and soft x-rays from a 10-nm electron beam at 580 MeV, was completed in 2012. Commissioning is in 4 progress and planned to continue through 2013 with interleaved user operation of ASTRID, until all beamlines 2 are fully operational on ASTRID2 at the end of 2013. The X [m] beta status of the project will be given together with comments 0 0 10 20 30 40 on some identified issues. Lattice position INTRODUCTION 15 ASTRID is the 140 nm emittance UV/VUV/soft x-ray light source at Aarhus University now in operation for 10 almost 20 years. Electrons are injected and accumulated at 100 MeV from a race-track microtron to more than 150 5 mA before being accelerated and stored with lifetimes in Y [m] beta excess of 100 hours [1]. 0 0 10 20 30 40 The new machine, ASTRID2 [2, 3, 4], is designed to produce close-to diffraction-limited synchrotron radiation in the same energy range. With an emittance of 10 nm, a Figure 1: Horizontal (X) and vertical (Y) betafunctions in relatively low lifetime of a few hours is expected. Hence, ASTRID2. the new facility will employ full-energy top-up operation converting ASTRID to become a 580 MeV booster. General Layout and Lattice The project started in august 2009 with an expected The lattice of ASTRID2 is a double bend achromat with completion date in December 2013 with all 5 beamlines six periods. The nominal beta-functions are shown in Fig. operational. The total project cost is around 5 M€ 1 with the full-drawn curves. The lattice includes in including upgrades of existing monochromators and addition to the two quadrupole families pole-face beamlines. Since the start of the project, an additional windings installed in all the vertically-focusing gradient beamline was funded and is being built. dipoles mainly for adjusting the vertical tune. Four families of sextupoles are installed in the machine for DESCRIPTION AND INSTALLATION chromaticity correction. Two beam-position monitors and Table 1 outlines some parameters of the ASTRID2 four corrector magnets are available in each sextant of the accelerator. machine for orbit correction. Table 1: ASTRID2 specifications Installation and Mechanical Alignment Quantity Value All magnets and most other systems are mounted on the 6 heavy girders, see Fig. 2. The girders were delivered Energy 580 MeV with aligned magnets before being transported to the Betatron tunes 5.185; 2.14 accelerator hall. Subsequently the girders were aligned, but at the same time an independent control of the Horizontal emittance ~10 nm magnets on the girders was performed. Next, all vacuum Natural chromaticity -6; -11 systems with bake-out systems were mounted by opening Design current 200 mA up the magnet yokes. After installation of all equipment, the concrete shielding wall was installed. Although the RF frequency 105 MHz reinforced concrete floor was poured a long time ago, Circumference 45.7 m subsidence’s after the installation of the heavy concrete shielding has been seen, and a realignment of girders is Dynamical aperture 25-30 mm planned. Hence the commissioning of the machine has up Beam power 1.1 kW to now been made with a somewhat mis-aligned machine possibly up to a few mm.

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ISBN 978-3-95450-122-9 02 Synchrotron Light Sources and FELs

Vacuum System use of thin insulating “ceramic paper” and flexible print foils is used. The vacuum system is a stainless steel system making After the initial heavy outgassing of the vacuum extensive use of NEG coating in all straight vacuum chambers, an average pressure of a few 10-9 mBar with 50 chambers. Additionally, the extruded aluminium vacuum mA of circulating current is obtained. One particular chambers in the insertion devices are NEG coated. The insertion device chamber is causing a pressure increase, bake-out system is mounted in situ, and in magnets the but still not affecting the lifetime too much.

Figure 2: The square ASTRID ring is seen at the lower left with the ASTRID2 storage ring at the right. Most of the concrete shielding in place around ASTRID2 with some beamline components installed too. The upper left shows a magnet girder with the red dipoles, the blue quadrupoles and the yellow sextupoles.

Radio Frequency System The cavity for ASTRID2 is an electron-beam welded capacitively-loaded copper cavity designed for the MAX IV project, but adjusted to the ASTRID and ASTRID2 frequencies of 105 MHz. A solid-state amplifier can deliver up to 8 kW of RF power. At present only ~1 kW has been supplied to the cavity as the final cooling system has just being finished. A Landau cavity will be installed later in 2013.

OPERATIONAL STATUS ASTRID booster operation including extraction has been operational since almost 2 years. Up to 4 mA has Figure 3: First top-up tests at 65 mA during 3 days. Two been accelerated and extracted into ASTRID2 with short accumulations to 150 mA are also seen. efficiencies up to 75 %. An additional loss originates from the extraction kicker rise-time in ASTRID. Although not With the short Touschek-dominated lifetime of the used yet, ASTRID operation also allows transfer of high ASTRID2 beam, top-up is mandatory. This operation has accumulated currents into ASTRID2. been implemented as demonstrated during several days in 2013 by JACoW — cc Creative Commons Attribution 3.0 (CC-BY-3.0) c Fig. 3. Several periods with 65 mA current are clearly ○

02 Synchrotron Light Sources and FELs ISBN 978-3-95450-122-9

A05 Synchrotron Radiation Facilities 65 Copyright MOPEA003 Proceedings of IPAC2013, Shanghai, China

visible. The drops in current are partly due to adjustments ASTRID2. The second initiative is the installation of and machine experiments taking place in the daytime of cooling of the ferrites by copper bars in thermal contact this period with the ferrite plates. The three bumpers are located in Although ASTRID is a relatively slow ramping three consecutive sextants with vacuum valves between. machine (25 s), Fig. 3 and 4 demonstrated early on a The first bumper has recently been modified with a strong sufficiently fast accumulation to achieve 150 mA reduction in the temperature, and the next two bumpers circulating beam. At the shown early test, the beam are presently being modified! accumulation was stopped and the beam only kept for a short period due to heating of the injection bumpers, see next section. Several functionalities and checks of the machine have been performed. For example, orbit correction has been demonstrated using the installed quadrupole shunts resulting in a correction of the orbit to better than 0.2 mm. Next, measurements of the beta-functions in the quadrupoles have been made using quadrupole shunting; see dots on Fig. 1. Variance with the nominal lattice is less than 20%. Figure 5: CAD model of the bumper magnet. The two improvements consisting of installation of the rf-screens and the copper cooling bars are clearly visible.

CONCLUSIONS The replacement of the old ASTRID light source with the new ASTRID2 machine is in progress. In 2012 and 2013, interleaved operation of ASTRID and ASTRID2 allows operation for users without any long dark periods. After minor modifications of some ASTRID2 components, ASTRID2 is well on the way to reach the design current at the end of 2013 using 5 beamlines. An Figure 4: First high-intensity accumulated beam in additional beamline with a new undulator for atomic and ASTRID2. Top-up at 150 mA was subsequently used. molecular physics has been funded and is being built.

LIMITATIONS AND IMPROVEMENTS ACKNOWLEDGMENT During the course of ASTRID2 commissioning, a Being a small acceleratory, the ASTRID2 project has couple of restrictions to the machine were detected and only been possible by extensive use of assistance from improvements to the machine are currently being made in many light-source laboratories in Europe. We deeply order to reach the design performance of the machine. acknowledge the involved colleagues. During the first few months of ASTRID booster operation, it was realized that the rubber plates mounted REFERENCES between the magnet coils and magnet yokes had to be [1] J.S. Nielsen, N. Hertel and S.P. Møller, IPAC’13, replaced. Otherwise, it was feared that the large forces Shanghai, MOPEA004. between coils and yokes would impact the epoxy [2] S.P. Møller, N. Hertel, and J.S. Nielsen, IPAC’10, Kyoto, insulation. This major operation of opening all 8 magnet p. 2487. yokes is presently on-going. [3] J.S. Nielsen, N. Hertel, and S.P. Møller, IPAC’11, San The injection bumpers, and also the ASTRID Sebastián, p. 2909. extraction kicker, were designed with the use of ferrite [4] S.P. Møller, N. Hertel, and J.S. Nielsen, IPAC’12, New Orleans, p. 1605. yokes inside the vacuum system and without any thin metal coating on the ferrite. It was realised during steady- state operation of the bumpers, that the bumpers stopped working above 70 mA circulating current. Heating of the ferrites in the bumpers above the Curie temperature is expected to be the cause of the problem, and the bumpers are now being modified by two initiatives. The first is

2013 byinstallation JACoW — cc Creative Commons Attribution 3.0 (CC-BY-3.0) of an RF shield, as seen in Fig. 5, at the

c entrance and exit of the bumper chambers. Such rf shields ○ has been installed in almost all other vacuum chambers in

ISBN 978-3-95450-122-9 02 Synchrotron Light Sources and FELs